Some mobile devices have features for determining a geographic location. For example, a mobile device can include a receiver for receiving signals from a global satellite system (e.g., global positioning system or GPS). The mobile device can determine a geographic location, including latitude and longitude, using the received GPS signals. In many places, GPS signals can be non-existent, weak, or subject to interference, such that it is not possible to accurately determine a location using the GPS functions of the mobile device. In such cases, the mobile device can determine its location using other technologies. For example, if the location of a wireless access gateway (e.g., a cellular tower) is known, and a mobile device can detect the wireless access gateway, the mobile device can then estimate a current location using a location of the detected wireless access gateway. The mobile device can choose how to determine its location based on whether GPS signals are available. On a mobile device, determining whether the GPS signals are available can take many seconds.